Fibre channel is a high-speed network technology used for data storage, providing high data transfer rates over long distances, thus allowing for high-speed storage interconnected over long distances. In a switched fibre channel-arbitrated loop (“FCAL”) network, Initiator to Initiator messages no longer traverse the whole network. The shortest route is taken which is one hop into a switch and then to the Initiator. In FCAL loop topology, any Initiator to Initiator messages are transmitted over all the links that make up that loop. FIG. 1 illustrates the known non-switched FCAL arbitrated loop topology. A ping or like status request communication between initiator A (102) and initiator B (104) traverses the entire loop and each disk in the loop. A ping command or like are sent in the direction of the denoted data flow (106 and 108).
FIG. 2 illustrates a known switched loop topology showing limited message function. The current routing of traffic between initiators is to take the shortest path, i.e., a hop into and out of a switch. In switched FCAL loop topology, messages between initiators (202 and 204) take the shortest route (206) and do not traverse the entire or network or all cascaded switches (208 and 210). This limits the function of the initiator to initiator message which was designed to detect any issue in the underlying network infrastructure. If this message does not traverse all the links in the network, it cannot detect any problems with these links.
U.S. Pat. No. 5,751,715 discloses an apparatus for accelerated Fiber Channel protocol handshaking and data exchange that divides a fiber Channel arbitrated loop architecture up into a plurality of arbitrated subloops. This patent teaches to bypass the subloops that do not contain source or destination.
U.S. Patent Application Publication No. 2004/0085974A1 discloses switching Fibre Channel Arbitrated Loop Systems between a plurality of Fibre Channel Loop devices, based in part on arbitrated loop primitives. This application disclosure is directed to arbitration and fairness algorithm used in switched loop topology. While it is disclosed that the system ensures device access fairness through techniques such as a rotating priority system, a counter to count the number of OPNs and priority based on port type, this patent application disclosure teaches to send the OPN directly to the target port, once arbitration is won, regardless of whether the entire switched network has been traversed or not.